Designed fabrication of lightweight SiC/Si3N4 aerogels for enhanced electromagnetic wave absorption and thermal insulation

The development of electromagnetic wave absorbers, which have widespread application prospects, requires new lightweight, multifunctional materials that can be used in harsh environments. Herein, ultralight SiC/Si3N4 aerogels are prepared by freeze-drying and carbothermal reduction reaction, and their microstructures were investigated by transmission electron microscopy, Raman spectroscopy, and X-ray absorption near-edge structure at the N K-edge. The result of morphology analysis indicates that the porous structure of SiC/Si3N4 aerogels are composed of SiC and Si3N4 nanowires. The optimal prepared SiC/Si3N4 aerogel possesses high absorption performance with a minimum reflection loss of − 25 dB and a wide effective absorbing bandwidth of 4.3 GHz (6.1–10.4 GHz) at a thickness of 3.97 mm. Such superior absorption performance is due to excellent impedance matching and enhanced polarization loss. Moreover, the SiC/Si3N4 aerogel is thermostable under air atmosphere below 1100 °C, which can be attributed to the presence of Si3N4. These achievements suggest that SiC/Si3N4 aerogel is promising candidate for electromagnetic wave absorption in harsh environment.